Technical Field
The present invention is directed generally to the field of flow sensors; specifically, to devices, systems and methods for continuous in situ monitoring of a rheologically complex fluid flow within a vessel (e.g., particulate and multiphase media). The present invention is functional to ascertain certain fluid flow parameters, such as flow rate, dynamic viscosity, fluid density, fluid temperature, particle density and particle mass, from flow sensor measurements.
Prior Art
In many engineering applications that deal with fluid flows, ascertaining certain fluid flow parameters from sensor measurements is fundamental. Examples of applications that deal with fluid flows include chemical processing and piping systems, food processing systems and oil pipelines. Fluid flows in such applications are typically rheologically complex (i.e., multiphase, elastic, shear thinning, fibrous, particulate and highly viscous) and/or chemically aggressive.
For example, the high shear wet granulation process widely used in the pharmaceutical industry involves a rheologically complex fluid flow. Because in-line control of the properties of the particulate fluid is crucial for producing a wet mass with specific desired characteristics, the wet granulation process depends on the accurate and precise computation of certain particulate fluid flow parameters.
Another example is related to the biotechnology industry. In certain biotechnology processes, cell culture techniques are leveraged to produce/manufacture therapeutic proteins and antibodies. An efficient and effective process analytical technology (PAT), based on reliable fluid flow sensor measurements, helps monitor cell growth in bioreactors, improves the throughput of the protein production and, therefore, reduces the cost of the drug.
Another example is related to lubricant, paint, ink or food production where the viscosity of the finished product affects product quality. Because most of these fluids are non-Newtonian and have viscosities that vary with the fluid flow velocity, dynamic in-line control of fluid viscosity is fundamental. Based on reliable fluid flow sensor measurements, the dynamic in-line control not only helps produce a final product with the correct properties but also increases the lifetime of the processing equipment. For example, if the viscosity of an ink flow falls outside the acceptable range, the dynamic in-line control can block valves and presses in the processing equipment. In the oil transportation industry, the presence of high viscosity phases (i.e., slugs) may affect the lifetime of the construction component.
Existing devices, systems and methods for ascertaining certain fluid flow parameters from in-line sensor measurements can be generally separated in two categories: non-intrusive and intrusive. The non-intrusive category may involve fluid flow interrogation with either electromagnetic or acoustic waves. The intrusive category may involve measuring devices/sensors in direct contact with a fluid flow such that the physical effect of the fluid flow on the device/sensor is leveraged to ascertain certain fluid flow parameters.
For example, prior art non-intrusive optical devices, systems and methods are capable of ascertaining certain fluid flow parameters from transparent fluids such as water and clear oils. They typically function by transmitting their optical signal through the window of a fluid flow vessel; however, in particulate and complex flows, the optical signal is scattered or absorbed by a thin layer of solid matter that is typically deposited on the surface of the window. Cleaning the window without interrupting the process significantly complicates the technology and risks contamination of the fluid.
Prior art non-intrusive acoustic devices, systems and methods are generally considered better suited for complex fluid flows but they also suffer from certain significant deficiencies. Many do not provide the desired measurement sensitivity for complex particulate fluid flows because the acoustic waves are scattered by the particles and/or the acoustic waves are reflected by the structural elements of the fluid flow vessel and/or sensor.
Prior art intrusive devices, systems and methods typically employ a sensor element directly contacting the fluid flow and comprising moving parts, e.g., a rotational meter, a turbine/propeller, a moveable vane, a mechanical oscillator, or a deformable diaphragm. These also suffer from significant deficiencies, especially in particulate and complex fluid flows, because solid matter deposits on the moving parts/joints rendering them inoperable. It is difficult and time-consuming to clean moving parts, and it also risks contamination of the fluid. Such maintenance procedures may also require interruption of the process, which may not be acceptable/practical for the specific engineering application. In addition, the moving parts introduce a risk of mechanical failure.
Vibrational viscometers are a popular prior art example in the intrusive category. A vibrational viscometer is a surface loaded system that responds to a thin layer of fluid surrounding an oscillating probe. Measurements by the vibrational viscometer depend on the surrounding fluid dampening the probe's vibration in proportion to the fluid's viscosity and density. Vibrational viscometers provide a sensitive measurement in many fluids but they often fail in particulate and multi-phase flows where deposition of the material on the probe surface changes the mechanical characteristics of the probe. Vibrational viscometers also have a relatively slow response time (e.g., several seconds) and are highly sensitive to external vibrations that can skew the measurements.
Target flow meters are another popular prior art example in the intrusive category. They operate on the principle that the amount of force generated by a fluid flow when passing a target (typically a disc) is related to the fluid flow velocity, density and viscosity. Therefore, most common target flow meters employ a target whose surface is oriented perpendicular to the direction of the fluid flow. The target typically is mounted to a stalk, and the stalk is generally affixed to a bendable balance beam configured to deflect/bend under the influence of the fluid flow. Strain gauges affixed to the balance beam, exposed to the fluid and/or recessed within a chamber, measure the degree of deflection/bend of the balance beam. Target flow meters have no moving parts, only a bending beam, and require minimal maintenance.
Prior art target flow meters, however, suffer from significant deficiencies. First, target flow meters have a very low sensitivity because of their inherent design, which must balance the need for a target with sufficient surface area with the need for a target flow meter that does not interfere with the fluid flow. Second, if the fluid flow is complex, viscous and/or particulate, particles in the fluid flow will accumulate on the target and skew the measurements. Third, the strain gauges and/or their protective means serve as a trap for particles and high viscosity components in a complex fluid flow, which alters the deflection/bend of the balance beam and skews the measurements.
For example, U.S. Pat. No. 6,253,625 issued on Jul. 3, 2001 to Samuelson et al. describes a target flow meter with a bendable stalk wherein the strain gauges are attached to the outside surface of the stalk. The strain gauges are, therefore, immersed in the fluid flow. To partially protect the strain gauges, the strain gauges are covered. Unfortunately, the cover creates a trap for fluid flow particles and high viscosity components in the complex fluid flow.
“The Design of a New Flow Meter for Pipes Based on the Drag Force Exerted on a Cylinder in Cross Flow” by C. Ruppel et al. (Transactions of the ASME, Vol. 126, July 2004, pp. 658-664) describes a device that consists of a flexible cylindrical beam mounted radially across a pipe. The reference describes that a load cell placed in a recess in the pipe wall measures the bending of the cylindrical beam by a fluid flow in the pipe. This approach eliminates the target by replacing it with a flexible cylindrical beam and requires that the cylindrical beam traverse the pipe. As in the previous example, the junction between the cylindrical beam and the pipe functions as a trap for particles and high viscosity components in a complex fluid flow. Moreover, because significant problems exist with sealing the force-sensing elements and electrical connections from the effects of the fluid flow, these devices experience a shortened lifespan. This is especially true in chemically aggressive and complex fluid flows.
U.S. Pat. No. 7,127,953 B1 issued on Oct. 31, 2006 to Yowell et al. describes a target flow meter with a rigid stalk attached to a flexible support base (which, therefore, constitutes a membrane). The strain gauges are attached to the surface of the membrane that is not exposed to the fluid flow. The movement of the rigid stalk is translated to the membrane and the deformation of the membrane is measured by the strain gauges. While this design may eliminate the disadvantage of the strain gauges being directly affected by the fluid flow, it introduces a new disadvantage: the deformation of the membrane is caused by both the drag of the fluid flow on the stalk and the fluid flow pressure.
Accordingly, there is a need for improved devices, systems, and methods for continuous in situ monitoring of a rheologically complex fluid flow within a vessel. Robust and reliable fluid flow sensors that are not susceptible to the above described deficiencies result in reduced maintenance costs, increased component service life and safer operations. It is to these needs, among others, that the present invention is directed.